Transcript plate boundaries - Ms. George`s Science Class

Plate Boundaries:
The Action is at the Edges!
The Earth’s Plates
• The earth’s crust is
made up of huge
tectonic plates
• These plates are
moved by convection
currents in the
Earth’s mantle layer,
like rafts floating on
thick liquid (like
toothpaste or
asphalt).
3 Types of Plate Boundaries
Plate boundaries are important to
understand because they are where
geological phenomena such as
earthquakes, volcanoes, and
tsunamis occur.
There are 3 main types of boundaries:
1. Divergent
2. Convergent
3. Transform (transform-fault)
1) DIVERGENT BOUNDARIES
• Almost all the Earth's new crust forms at
divergent boundaries, but most are not
well known because they lie deep
beneath the oceans.
• Divergent boundaries are zones where
two plates move away from each other,
allowing magma from the mantle to rise
up and solidify as new crust.
DIVERGENT BOUNDARIES
• Divergent boundaries most often occur
on the ocean floor along the mid-ocean
ridges.
Mid-Atlantic Ridge
• The Mid-Atlantic
Ridge, which splits
nearly the entire
Atlantic Ocean north
to south, is probably
the best-known and
most-studied
example of a
divergent plate
boundary.
Iceland sits upon the Mid-Atlantic Ridge
A Divergent Boundary
• The western side of
Iceland sits on the North
American Plate and is
moving toward the west.
• The eastern side of
Iceland sits on the
Eurasian Plate and is
moving toward the east.
Thingvellir
National Park
• On my trip to Iceland in
July 2006, I visited
Thingvellir National
Park, located on the
Mid-Atlantic Ridge!
Thingvellir
• I walked from
the North
American Plate
to the Eurasian
Plate
Iceland
Geological
Activity
• There are many
amazing sites in
Iceland like this
boiling mud pit.
• The hot magma is so
close under the
earth’s crust that it’s
a danger to visitors,
who must obey the
signs!
Intense sulfur smell !
2) CONVERGENT BOUNDARIES
•
•
•
•
Occur when plates collide or push against each other.
Sometimes one plate slides below the other.
This is called subduction.
As the more dense plate sinks into the mantle, it
melts. The magma that forms from this melting plate
may slowly rise & produce volcanoes.
CONVERGENT BOUNDARIES
• Sometimes the plates buckle and rise to
form mountains.
• The Himalayan mountain range formed this
way—when two plates collided.
Example: Himalayan Mt. Range
• 40-50 million years ago, two large
landmasses, India and Eurasia,
collided.
• The two plates had the same
density, so one could not sink
below the other.
• The pressure caused the plate
edges to thrust upward toward
the sky.
• The Himalayan mountains are
still growing at a rate of 1 cm.
per year.
3) TRANSFORM BOUNDARIES
• At transform boundaries, plates grind past
each other side by side.
• This type of boundary separates the North
American plate from the Pacific plate
along the San Andreas fault, a famous
transform plate boundary that is
responsible for many of California's
earthquakes.
SAN ANDREAS FAULT
Diagram the Three
Different Plate Boundaries
1. Draw large arrows showing the direction
the plates are moving at the 3 different
boundaries.
2. Write down an example of a location of
each type of boundary.
Divergent
Example: __________________________________
Convergent
Example: ___________________________________
Transform (Transform-Fault)
Example: ___________________________________